Photosensitive material



United States Patent PHOTOSENSITIVE MATERIAL N Drawing. Filed May 5, 1955, Ser. No. 506,369

10 Claims. (Cl. 96-7 5) This invention relates to a type ofphotosensitive material commonly used as an intermediate reproductionmaterial in the drafting art. It can be used to make duplicate tracingsfrom which additional prints can be made by the ordinary reproductionmethods. The particular type of material to which the invention relatesis made by coating a suitable light transmitting base such as tracingcloth, tracing paper and other transparentized bases or naturallytransparent or translucent bases with a colloid layer containing asilver halide and an agent capable of hardening a colloid under theinfluence of light. The base for this type of photosensitive materialmay for example be tracing cloth which has been coated with a lacquer tomake it waterproof, then coated with a subbing layer and finally coatedwith the light sensitive layer described above. The purpose of thesubbing layer is to promote adhesion between the light sensitive layerand the waterproofed base material. The substratum also afiects somecharacteristics of the sensitive layer, such as printing speed,gradation .(contrast keeping .quality, .etc.

Photosensitive materials of the type described are'exposed to lightunder anegative original which may be a brownprint made from a tracingor a drawing on transparent paper. After exposure, the material iswashed with water to remove thecolloid layer -from the unexposed areasand then developed with :a photographic developing solution to form ametallic. silver relief image of the exposed areas which usually appearsblack; v

For the most part, chromates have been used as the light sensitivehardening agent for the colloid in the photosensitive material of thistype known in the art. However, Patent No. 2,663,640, which issued to M.K. Reichel and W. Neugebauer on December 22, 1953, discloses the use ofdiazido compounds as the light hardening agent in this type of material.

The subbing layer used in this type of material includes a proteincolloid such as glue, gelatin and the like. It has been a practice toadd a small amount of formaldehyde to increase the water resistance ofthe colloid and thereby improve the adhesion of the photosensitive layerto the base during the processing of the material to form the imagethereon. Despite the use of this formaldehyde, one of the most effectivecolloid hardening agents known, it has been found that the adhesion ofthe photosensitive layer varies considerably from batch to batch inproduction which has been a great handicap in the commerical use of thistype of reproduction material. In addition, the formaldehyde isobjectionable because of its unpleasant odor.

Now it has been found that improved results are obtained by eliminatingformaldehyde from the subbing and using a small amount of zirconiumsalt. The zirconium salt may either be used in a solution which isapplied to the subbing layer or the zirconium salt may be incorporatedwith the protein colloid and coated on the base material therewith toform the subbing layer.

The principal objects of the present invention are to 2,942,915 PatentedJune 28, 1960 2 improve intermediate reproduction materials having alight sensitive layer including a colloid, a silver halide and alight-hardening agent by using a zirconium salt carried by the subbingfor such layers and eliminating the objectionable effects resulting fromthe use of formaldehyde in such materials.

The principal zirconium salt which has found use according to thepresent invention is zirconium acetate having the approximate formula HZrO (C H O However, other zirconium salt may be used such as zirconiumoxychloride Zr O CI .6H O ammonium zirconyl carbonate, (NH ZrOH(CO .2H Oand zirconium sulphate, Zr(SO .4I-I O. When some of these salts areused, it may be necessary to adjust the pH. The best results areobtained if the pH of the wash solution containing the zirconium salt isadjusted to fall within a range close to the isoelectric point of thecolloid used. In the case of a particular gelatin suitable for use insubbing layers, the pH of the wash solution used therewith should bebetween 4 and 6. It is also necessary to balance the ratio between thewater and organic solvent used in the wash solution since if thepercentage of organic solvents is toogreat, the zirconium salt may tendto separate out in the form of a gel. I

The protein colloids which are useful in the subbing of the presentinvention are gelatin, glue, albumin, casein and zein.

The waterproofed layer which is applied to protect the tracing cloth maybe a nitrocellulose lacquer or other types of lacquers may be used. Awide variety of resins may be incorporated in the waterproofed layer ormultiple resin coats may be used such as vinyl resin coating followed bynitrocellulose both of which together may be considered to be thewaterproofed layer. it is also C? tomary to apply wateiproofed layers tothe back side of the material. Additional layers may also be applied tothe back side in ,order to make the properties of this sidesimiliar tothose of thephotosensitiye side of the material in order to preventcurling.

' The practice of the' invent-ion'is illustrated by thejfollowingexamples:

' Example I A waterproofedtracing cloth was coated with a subbing layerof the following formula:

grams gelatin 8800 cc. methyl alcohol 1600 cc. glacial acetic acid 100cc. Water Ethyl alcohol and/or acetone may replace all or part of themethyl alcohol in the above formula. Before coating the photosensitivelayer on this subbing it was treated with a wash solution made upaccording to the following formula:

20 cc. zirconium acetate solution (this solution contains the equivalentof 14% ZIO2) 350 cc. water 600 cc. organic solvents selected from methylalcohol,

ethyl alcohol, acetone and methyl ethyl ketone Small percentages ofwetting agents and flow agents may also be incorporated in this formula.

The material was then coated with a light sensitive coating made upaccording to the following formula:

To an emulsion consisting of:

base.

- oz. by weight of potassium chloride in distilled water Example II Atracing cloth provided with a waterproofed lacquered coating was coatedwith a snubbing layer made according to the following formula:

120 grams gelatin 9500 cc. methyl alcohol 1500 cc. glacial acetic acid150 cc. water 120 cc. zirconium acetate solution containing theequivalent of 14% Zr Ethyl alcohol, acetone and methyl ethyl ketone maybe used to replace all or part of the methyl alcohol in the aboveformula. Small quantities of wetting agents or flow agents may also beadded to this subbing solution.

The base material provided with this subbing was coated with the samephotosensitive material described in Example I and reproductions madewith the material showed the same excellent properties and inparticular, the same outstanding adhesion of the image areas to theExample Ill The waterproofed tracing cloth material subbed in accordwith Example II was coated with a light sensitive composition exactlythe same as that disclosed in Example I except that 2 oz. by weight of4,4'-diazido-sti1- 7 bone, 2,2-disulfonic acid sodium salt dissolved in10 liquid ounces of distilled water were substituted forpotassium'bichromate solution used in Example I.

' Reproductions made with this material exhibited greater adhesion ofthe image areas to the base than relief image comprising a base, asubbing layer including gelatin and a zirconium'salt on said base, alight sensitive emulsion layer including a silver halide, photographicglue, and a light hardening agent selected from the group of dichromatesand diazido compounds, said light sensitive layer being coated on saidsubbing layer whereby when the light sensitive layer is exposed to lightthe exposed portions of said light sensitive layer adhere securely tothe subbing layer.

2. The invention according to claim 1 in which the base is of lighttransmitting material.

3. The invention according to claim 2 in which a waterproofing layer isprovided on the base.

4. The invention according to claim 3 in which the waterproofing layeris nitrocellulose, the base is tracing cloth, the zirconium salt iszirconium acetate, and the hardening agent is a bichromate.

5. The invention according to claim 1 in which the hardening agent is abichromate.

6. The invention according to claim 1 in which the hardeningagent is asalt of 4,4'-diazido-stilbene, 2,2- disulfonic acid. I

7. The invention according to claim 1 in which the subbing layer-has apH of 4 to 7.

8. The invention according to claim 1- in which the pHlof the, subbinglayer falls close to the isoelectric point of the gelatin.

. 9. The invention according to claim 1 in which the zirconium salt isapplied by a wash to the subbing layer. 10. The invention according toclaim 1 in whichthe zirconium salt is incorporated in the subbing layerprior to coatingon the base.

References Cited in the file of this patent UNITED STATES PATENTS2,327,004

OTHER REFERENCES Journal of Photography, May 25, 1951, pages 267 and268, V01. XCYHI, NO; 47491. i i V

1. A PHOTOSENSITIVE MATERIAL FOR PRODUCING A DARK RELIEF IMAGECOMPRISING A BASE, A SUBBING LAYER INCLUDING GELATIN AND A ZIRCONIUMSALT ON SAID BASE, A LIGHT SENSITIVE EMULSION LAYER INCLUDING A SILVERHALIDE, PHOTOGRAPHIC GLUE, AND A LIGHT HARDENING AGENT SELECTED FROM THEGROUP OF DICHROMATES AND DIAZIDO COMPOUNDS, SAID LIGHT SENSITIVE LAYERBEING COATED ON SAID SUBBING LAYER WHEREBY WHEN THE LIGHT SENSITIVELAYER IS EXPOSED TO LIGHT THE EXPOSED PORTIONS OF SAID LIGHT SENSITIVELAYER ADHERE SECURELY TO THE SUBBING LAYER.